Which interaction stimulates the activation of a naive B cell?

The activation of a naive B cell is critically dependent on its interaction with helper T cells. When a B cell encounters an antigen, it can present pieces of that antigen on its surface using major histocompatibility complex (MHC) class II molecules. The specific interaction that stimulates the activation of the naive B cell occurs when a helper T cell binds to this complex. This binding is facilitated by the T cell receptor on the helper T cell recognizing the peptide-MHC class II complex on the B cell.

Moreover, this interaction leads to the secretion of cytokines by the activated T cell, which further enhances the proliferative and differentiative response of the B cell. This process is essential for ensuring a robust and specific response to the antigen, ultimately enabling the B cell to produce antibodies and contribute to the adaptive immune response.

Other interactions noted in the question do not directly lead to the activation of naive B cells. For example, MHC class I primarily presents antigens to cytotoxic T cells rather than B cells, while natural killer cells are involved in innate immunity and do not activate B cells. Direct interaction with pathogens may lead to some form of response but typically does not involve the specific helper T cell-mediated activation required for naive B cell activation.